The present invention relates to systems for injection supply of LPG for internal-combustion engines.
The invention relates in particular to a system for injection supply of LPG, of the type comprising a hollow structure having a top opening closed by a service flange that carries means for the hydraulic and electrical connections of the tank to the fuel-supply system.
Tanks of the type specified above are described, for example, in the European patent EP-B-0 922 851 in the name of the present applicant and in the corresponding U.S Pat. No. 6,050,237.
In tanks of the above type so far produced, the aforesaid means for the hydraulic and electrical connections of the tank to the supply system include:
a first hole for connection with the pipe for delivery of LPG to the injectors of the fuel-supply system (preferably served by a distribution manifold);
a valve assembly associated to said first connection hole, including a flow-limiting valve and a shutoff solenoid valve;
a second hole for connection with the pipe for flow back into the tank of the excess LPG fed to the injectors;
a return valve associated to said second connection hole;
a solenoid valve for filling of the tank;
a safety valve for preventing the pressure inside the tank from exceeding a pre-set threshold value; and
an electrical connection device for electrical supply to the electrically operated devices present inside the tank.
Again according to the prior art described above, set inside the tank are an electrically operated pump and a level-sensing device.
One purpose of the present invention is to simplify the structure of the tank and in particular the structure of the aforesaid service flange. A further purpose is to improve the efficiency of the various parts associated to the tank, with particular regard to the reliability and precision of operation of the level-sensing device.
With a view to achieving the above purposes, the subject of the invention is a tank having all the characteristics that have not been mentioned above and being moreover characterized in that the aforesaid valve assembly including the shutoff valve and the flow-limiting valve, the aforesaid return valve and the aforesaid filling valve each have a structure set entirely underneath the service flange and fixed against the bottom surface of the latter, without having any parts mounted via through holes of the flange. Preferably, each of said assemblies has an attachment flange which is fixed by means of screws underneath the service flange.
Thanks to the above-mentioned characteristics, the structure and conformation of the service flange are extremely simplified as compared to those adopted in the known solutions.
In addition, with a view to achieving the further purpose specified above, the tank according to the invention is moreover characterized in that the aforesaid sensor device is of a capacitive type and has a structure rigidly connected to the structure of tank, independently of the aforesaid service flange. Thanks to this characteristic, a better precision of the sensor is achieved, without moreover having to resort to the use of a float, unlike the case of known solutions which, instead, do use a sensor with a float. The said float must in fact be made of a material with a low specific weight, given that LPG has a specific weight which is approximately one half that of water. Consequently, in the case of known solutions the risk arises that the light material of the float may collapse on account of the pressure to which it is subjected, thus reducing in volume. The use of the sensor of a capacitive type according to the invention provides a radical solution to said problem.
Preferably, moreover, also the electrically operated pump which is set inside the tank is rigidly connected to the structure of the latter, unlike what occurs in the case of known solutions, in which the pump is secured to the service flange.